Hitherto, electrophotographic image forming devices have used cleaning devices, which are cleaning means, to remove unnecessary untransferred residual toner adhering on surfaces of image bearers such as photoconductors, which are cleaning target members, after toner images are transferred onto transfer paper or intermediate transfer media.
Well-known cleaning devices use strip-shaped elastic blades as cleaning members, because the strip-shaped elastic blades can typically make the configurations simple and have excellent cleaning performances. Each of the elastic blades is formed of an elastic body such as a polyurethane rubber. With a base end of the elastic blade supported on a supporting member, a projecting end edge portion is pressed against a peripheral surface of the image bearer to block, scrape off, and remove toner remaining on the image bearer.
With the elastic blade formed of polyurethane, however, as illustrated in FIG. 6A, a frictional force between an image bearer 123 and a cleaning blade 62 increases to draw the cleaning blade 62 in a direction in which the image bearer 123 is moved, to cause a projecting end edge portion 62c of the cleaning blade 62 to curl. When cleaning is continued in the state that the projecting end edge portion 62c of the cleaning blade 62 is curling, a local wear occurs at a position that is on a blade projecting end surface 62a of the cleaning blade 62 and is apart from the projecting end edge portion 62c by some micrometers as illustrated in FIG. 6B. When cleaning is further continued in this state, the local wear grows for the projecting end edge portion 62c to be lost finally as illustrated in FIG. 6C. When the projecting end edge portion 62c is lost, toner cannot be cleaned well and a cleaning failure may occur. Reference numeral 62b denotes a vertical surface on the projecting end edge portion.
Hence, in order to suppress curling of the projecting end edge portion of the cleaning blade, there has been a need to provide the projecting end edge portion with a high hardness to make the projecting end edge portion less deformable. As a method for providing a projecting end with a high hardness, Patent document 1 discloses a method of impregnating a surface and an internal portion of a blade with an ultraviolet-curable resin to provide a high hardness and make the projecting end edge portion less deformable both initially and over time.
As a method for applying an impregnation treatment to provide a surface and an internal portion of an elastic blade with a high hardness, there is a method of impregnating a urethane rubber, which is the base material of the elastic blade, with an ultraviolet-curable resin from a surface of the urethane rubber, removing the resin excessively remaining on the surface of the blade after the impregnation, and then curing the resin by ultraviolet irradiation. In this method, the step of removing the resin excessively remaining on the surface of the blade is performed by an operation of wiping the blade in the longer direction with a solvent. However, the solvent may extract not only the resin on the surface of the urethane rubber but also the resin that has impregnated the internal portion. Because the extracted resin adheres to non-woven fabric soaked with the solvent used for the wiping, the concentration of the resin adhering to the non-woven fabric increases as the wiping goes on, to weaken the capacity for extracting the resin. As a result, the wiping capacity is uneven in the longer direction of the blade to cause a gradient or unevenness in the amount of the resin to remain in the internal portion of the blade, and this has been confirmed to appear as a severe hardness gradient or hardness unevenness after final curing. A blade that has a hardness gradient or hardness unevenness in the longer direction is unable to apply a pressure on an image bearer uniformly in the longer direction and allows part of toner to slip through, to cause a cleaning failure. Further, the impregnated resin is extracted in a large amount when kept for a long time in contact with the solvent used for the wiping, to fail in providing a high hardness even if the resin is cured. This causes the projecting end edge portion to curl, leading to slip-through of toner and a cleaning failure.
Furthermore, as described in Patent documents 2 and 3, a cleaning blade produced through impregnation and a curing treatment has protrusions on a surface of the cured layer unless the residue on the surface of the blade is uniformly removed after the impregnation treatment. While cleaning residual toner on an image bearer, such a cleaning blade allows the toner to slip through from around the protrusions, to cause a cleaning failure. After impregnation of an isocyanate compound, Patent document 2 employs a step of blowing hot air to blow away an excessive portion of the isocyanate compound and further wiping off the isocyanate compound with a solvent for sufficient removal. Not only is the treatment with hot air alone insufficient, but wiping off with a solvent produces a hardness difference in the longer direction of the blade as described above.